Maternal smoking and childhood asthma

The role of maternal smoking as a causal factor for the incidence of childh ood asthma is still not clearly established. It was investigated among 3- a nd 4-year-old-child incident cases confirmed by a 6-year follow-up (n = 294 ) and cases who no longer had symptoms after diagnosis (n = 110). The study took place in Montreal, Canada, between 1988 and 1997. Persistent and tran sient cases were compared with their respective controls from the original case-control study of incidence. The odds ratio for heavy maternal smoking adjusted for known risk factors for asthma was 3.84 (95% confidence interva l: 1.68, 8.76) among persistent cases and close to one among transient case s.